Hetero-Polyionic Hydrogels Enable Dendrites-Free Aqueous Zn-I₂ Batteries with Fast Kinetics

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable aqueous zinc-iodine (Zn-I₂) batteries are promising energy storage devices.
• Key challenges include soluble polyiodide shuttling and zinc dendrite growth, hindering commercialization.

Purpose of the Study:

• To design a hetero-polyionic hydrogel electrolyte for Zn-I₂ batteries.
• To address polyiodide shuttling and zinc dendrite issues for improved battery stability and longevity.

Main Methods:

• Development of an iodophilic polycationic hydrogel (PCH) for the cathode to manage iodine species.
• Incorporation of a polyanionic hydrogel (PAH) for the zinc anode to ensure uniform ion flux and prevent corrosion.
• Testing of Zn symmetric cells and Zn-I₂ full cells with the novel hydrogel electrolyte.

Main Results:

• Zn symmetric cells exhibited exceptional cycling stability over 3000 hours at 1 mA cm^-2 and 800 hours at 10 mA cm^-2.
• Zn-I₂ full cells demonstrated remarkable longevity with a capacity decay of only 0.008 ‰ per cycle over 18,000 cycles at 8 C.
• The hetero-polyionic hydrogel electrolyte effectively mitigated shuttle effects and uniformized Zn²⁺ deposition.

Conclusions:

• The designed hetero-polyionic hydrogel electrolyte significantly enhances the cycling stability and lifespan of aqueous Zn-I₂ batteries.
• This approach offers a viable strategy for developing long-life conversion-type aqueous batteries.
• The study provides insights into advanced hydrogel electrolyte design for next-generation energy storage systems.